1. Technical Field
The disclosure of the present invention generally relates to a method for healing a phase-change memory device and the applications thereof, and more particularly to a method for healing a phase-change memory device with chalcogenide-based based material or other suitable material and the applications thereof.
2. Description of the Related Art
Phase-change based memory materials, such as chalcogenide-based materials and similar materials, can be caused to change phase between an amorphous phase and a crystalline phase by application of electrical current at levels suitable for implementation in integrated circuits. In comparison with the crystalline phase, the amorphous phase is characterized by a higher electrical resistivity which can be readily sensed to indicate data. These properties may cause the chalcogenide-based materials suitable for serving as programmable resistive material to form nonvolatile memory circuits, which can be read and written with random access, e.g a phase-change memory devices.
A phase-change memory device can be read and written with random access by the transformations between the amorphous phase and the crystalline phase occurring on the chalcogenide-based materials disposed in the active area of the phase-change memory device. For example, the phase of the chalcogenide-based materials (phase-change materials) disposed in the active area of the phase-change memory device may be transformed from the amorphous phase to the crystalline phase when a low-voltage electric pulse is applied to the active area of the memory cells, whereby the resistance states of the memory cells involved in the phase-change memory device may be transformed either from an initial state 103 or from a high resistance state 102 to a low resistance state 101. The process of transforming resistance state form high to low is referred as a set process. Alternatively, the low resistance state 101 of the memory cells may be transformed to the high resistance state 102 again by applying a high-voltage electric pulse to the active area of the memory cells in order to transform the crystalline phase of the chalcogenide-based materials to the amorphous phase. The process of transforming resistance state form low to high is referred as a reset process.
FIG. 1 is a distribution graph of memory cells with various resistance states in a prior art phase-change memory device, wherein each of the memory cells may either have a high resistance state 102 or have a low resistance state 101 without overlapped with the high resistance state 102 by the set process or the reset process. There is a gap between the highest resistance R1 of the high resistance state 102 and the lowest resistance R2 of the low resistance state 101 used to determine what the resistance state a memory cell has. The data stored in a memory cell may be referred as “0” when the resistance state of the memory cell is determined less than a threshold limit value (threshold resistance) 103, and the data may be referred as “1” when the resistance state of the memory cell is determined greater than the threshold resistance 103.
However after a plurality numbers of read, set and reset operations are carried out, degradations of the phase-change materials may occur due to the electrical energy applied to the phase-change materials during the set/reset operations, the operation temperature and/or the arrangement of the memory cells. Such that the electrical properties, such as resistance state, relationship between the resistance and the current etc., of the phase-change material may shift from an initial state. For example, the phase-change materials disposed in the active area of the memory cells that has the high resistance state 102 may be recrystallized due to the electrical energy and the thermal stress applied to the phase-change materials during the set and reset operations, and the resistance of the phase-change materials may be reduced gradually, whereby it requires more operation current and bit error of the phase-change memory device may occur when the lowest resistance R2 of the low resistance state 102 is reduced to a level less than the threshold resistance 103.
Therefore, there is a need of providing an improved method for healing a phase-change memory device and the applications thereof to obviate the drawbacks encountered from the prior art.